Slide-valve



UNITED :STATES PATENT @EHC-E.

JAMES MILLHOLLAXD, OF READING, PENNSYLVANIA.

stirs-verve.

Specification of Letters Patent No. 30,1510, zdated September 25, 18530.

T o all whom fit may concern:

Be it known that I, JAMES MILLHOLLAND, of Reading, Berks county,Pennsylvania, haveinvented certain newV and useful Improvements inBalanced Slide-Valves for Steam-Engines; and I do hereby declare thefollowing to be a full, clear, and exact description of the same,reference being had to the accompanying drawing and to the letters ofreference marked thereon.

My invention relates to improvements in the construction of that classof slide valves, in which a cap, fittedto the valve, and bearing againstthe underside of the steam chest, is used for the purpose ofcounteracting the pressure of steam on the valve, and thereby avoidingthe inordinate and detrimental friction common to ordinary slide valves;and my improvements consist, firstly of a cap with an inner and outerannular flange, the inner flange being so adapted to a hub on the valve,that the said hub shall resist all lateral strains imparted to the cap,having a spiral spring used for raising the cap undisturbed, the wholebeing applied, and arranged in respect to, the valve substantially asdescribed hereafter.

My invention further consists in the peculiar application explainedhereafter, of one, or more metallic rings, forming such a packingbetween the cap and the valve as will allow the former to movevertically on the latter with freedom, and still form an efficient steamtiglit joint.

In order to enable others skilled in the art to make and use myinvention, I will now proceed to describe its construction andoperation.

On reference to the accompanying draw ing which forms a part of thisspecication, Figure l is a perspective view of a slide valve with myimprovement; I`ig. 2, a transverse section of the same; Fig. 3, a planview of Fig. 2; Fig. 4C, a section on the line l, 2 Fig. 2; Fig. 5, aplan view of Fig. 4; Fig. 6, a detached view of the spring whichintervenes between the cap and the valve; Fig. 7, a detached perspectiveview of one of the packing rings, &c.; Fig. 8, an enlarged sectionalview illustrating the mode of applying the packing rings.

Similar letters refer to similar parts throughout the several views.

The lower portion of the valve is formed in a manner similar to that ofordinary slide valves, there being the usual chamber (A) and flanges (a,a) adapted to the openings in the face of the steam cylinder, and thefront edge of the valve having two lugs (Y), to which the valve spindleis connected. On the top 0f this lower portion of the valve is acircular plate or disk (B) from which project the central hub c, andannular flange l both disk, hub and flange being arranged concentricallywith each other, and occupying the position in respect tothe valve,illustrated in Figs. 3 and 5.

(C) is the cap consisting `of a circular plate or disk, having an innerannular flange (c) and outer annular flange The inside of the innerflange of the cap is arranged to lit snugly to, but so as to have a freevertical movement on the central hub (c) of Athe valve; the inside ofthe outer annular flange of the cap being a short distance from theoutside of the annular flange of the valve, as best observed onreference to Fig. 2.

In the space between the flange (e) of the cap and the flange (d) of thevalve, is situated the spring which is of the spiral form illustrated byFig. 6. This spring is made of'cast iron, by first turning a hollowcylinder of that metal, and then cutting a spiral groove along andentirely through the cylinder.

In the loutside of the annular flange (d), of the valve are cut twoannular grooves (it, h) Fig. at, one groove being a short distance abovethe other, and into each of these grooves is fitted a packing ring aperspective view of which is shown in Fig. "7. Each ring is made of castiron turned perfectly true, and afterward severed at one point, thetendency of the ring to expand when thus severed being sufficientlypowerful to cause the outer edge of each ring, to bear with the requiredforce against the inside of the annular flange (f) of the cap.

It should be understood that the underside of the steam chest coveiI isplaned perfectly true and smooth as is also the annular strip (j) on thetop 4of the cap (C) which is caused by the spiral spring D to bearagainst the underside of the steam chest with sullicient force tomaintain a steam tight oint at this point without creating inordinatefriction.

By making the area of the cap (C) equal in extent to the area of theface of the valve,

it will be evident that the enormous and detrimental pressure of steam,which, but for the cap, would be exerted on the valve, 1s

counteracted; in other words the valve is an antipressure or balancevalve, the elasticity of the spring (D,) tending as it does to force thecap and the valve apart, being of itself sufficient to maintain the faceof the valve in close steam tight Contact with the .face of the steamcylinder, and the cap in close steam tight contact with the underside ofthe steam chest cover.

In some instances the valve face and cap, may be so proportioned thatthe area of the former shall exceed that of the latter, in which casethere will be a proportionate excess of pressure of steam on the valve,tending to maintain the latter close to its seat, independent of thetendency of the spiral spring to accomplish the same end.

The packing` rings (i, are placed in their proper position by expandingthem sufficiently to allow them to slip over the annular flange of thevalve, and depressing them until they coincide with the annular grooves(it, it) within which they will at once take their proper places.

It will be observed on reference to the enlarged sectional view, Fig. 8,that the upper side of each of these annular recesses is beveled inward,so as to resent a somewhat vsharp edge on the outsi e for the upper sideof the packing rings to' bear against.

As the tendency of the cap is to move upward it will carry the ringswith it, and consequently cause these rings to bear hardest against thisnarrow bearing formed by the above mentioned bevel of the annulargrooves (7L, 71.), a closer fit will therefore be insured at this point,than if the ring had a bearing extending the entire depth of thegrooves. By fitting the annular projection e of the cap over the centralhub (0) of the valve, the cap and valve become integral parts of eachother in every respect excepting that one has a free, vertical movementindependent of the other, so that whatever lateral strains may beimparted to the cap during the reciprocating motion of the valve theyare resisted by the central hub only, the spiral spring and packingrings remaining undisturbed. It will be observed that there are severalopenings (7c, lo) in the top of the cap (C), there are also openings inthe steam chest cover so that the vspace between the cap and the valveis open to the external air, the access of steam to this space beingexcluded by the rings (i, z'), the two ends of which are so nicelyfitted together as to form a tight joint.

Although I prefer the use of two packing rings, I have found in practicethat one ring only is sufficient for the purpose.

My improvement may be readily applied to slide valves of the ordinaryconstruction, the circular plate (B) with its central hub (c) andannular flange l being bolted or otherwise secured to the top of thevalve.

I wish it to be understood that I do not claim broadly the use of a capfltted to the top of the valve, and bearing against the under side ofthe steam chest for the purpose of reducing the pressure of steamA onthe valve, nor do I claim the use of severed rings for steam tightpacking, but

I claim as my invention, and desire to secure by Letters Patent:

l. The cap (C) with its annular flanges and (e), and the spiral spring(D), or its equivalent, when the said flange e is so adapted to the hub(c) of the Valve, that the said hub shall resist all lateral strainsimparted to the cap, and when the whole is applied and arranged inrespect to the valve substantially as specified.

2. The within described application of one or more severed metallicrings (i, fitted into grooves in the annular flange (d) of the valve,and bearing against the annular' flange (f) of the cap as and for thepurpose set forth.

3. Beveling the upper sides of the annular recesses (72., L) so as topresent a sharp edge for the purpose specified.

In testimony whereof, I have signed my name to this specification, inthe presence of two subscribing witnesses.

JAMES MILLHOLLAND.

fitnesses HENRY HowsoN, CHAs. HowsoN.

